Starch is a complex carbohydrate composed of two types of polysaccharide molecules, amylose, a mostly linear and flexible polymer of D-anhydroglucose units that are linked by alpha-1,4-D-glucosidic bonds, and amylopectin, a branched polymer of linear chains that are linked by alpha-1,6-D-glucosidic bonds.
Research literature indicates that starches high in fiber have numerous beneficial effects, including colonic health and a reduced caloric value. In addition, the starches may provide reduced meal carbohydrate content, reduced glycemic and insulimic responses, impact satiety and contribute to sustained energy release, weight management, control of hypoglycemia, hyperglycemia, impaired glucose regulation, insulin resistance syndrome, type II diabetes mellitus, and improved athletic performance, mental concentration and memory.
It is known that certain starch processing operations including chemical, enzymatic, and physical modifications, may increase the dietary fiber content of starch. Unfortunately, the dietary fiber content of many of these starches does not withstand the harsh conditions of processing, particularly extrusion, resulting in extruded products with substantially reduced fiber. In order to keep the total dietary fiber content high, either alternative sources of fiber have been used, or the amount of starch has been increased to allow for such processing loss. Unfortunately, alternative sources of fiber often do not provide the same health benefits which are recognized for high fiber resistant starches, have a negative effect on final product functional properties, and/or present a need to significantly change processing conditions. Further, use of high amounts of starch can be deleterious to the organoleptic properties of the product and does not present an economical solution.
Surprisingly, it has now been discovered that starch chemically crosslinked with sodium trimetaphosphate or a combination of sodium trimetaphosphate and sodium tripolyphosphate and heat-moisture treated may be extruded under a variety of different shear levels, or otherwise harshly processed, yet retain over 50% of its total dietary fiber content.